In many applications, such as aerospace applications and the like, it is desirable to manufacture thin metallic components. The machining of such thin metallic components as monolithic structures has largely replaced sheet metal assembly operations for aluminum components, for example. A stress-relieved plate stock workpiece is machined layer by layer using a relieved shank tool or the like. The workpiece is machined where it is stiff, and thin sections are left behind—the workpiece deriving its stiffness from the not-yet-machined sections.
However, such techniques have not really proven useful for difficult-to-machine and expensive materials, such as titanium and nickel alloys, for several reasons: (1) these materials are not amenable to use in stress-relieved plate stock; (2) these materials are far too expensive to necessitate all the excess that would be required; and (3) tool wear requirements with these materials demand small radial depths of cuts (restricting contact times and lowering maximum temperatures).
Thus, there have been numerous attempts to manufacture thin components made of difficult-to-machine and expensive materials utilizing near-net shape forming, near-net shape casting, and additive processes, without prior component and manufacturing process analysis. The structures made utilizing such techniques still need to be machined to reach final geometry, but they are so thin that they make stable, accurate machining difficult. As a result, some have resorted to innovative fixturing techniques to hold these thin workpieces during machining.
In other words, the machining of thin parts and the like is often difficult because such parts have insufficient static and dynamic stiffness. Accurate thin parts and the like are difficult to achieve due to the effects of clamping forces, cutting forces, residual stresses, and chatter. Thus, bulk structures have been used to support such parts during machining, but do not comprise constituents of the finished components, again, without prior component and manufacturing process analysis.
Conventional bulk and near-net shape structures simply do not work well in the machining of thin parts, as, in order to provide such parts with sufficient static and dynamic stiffness, too much material must be removed, resulting in unnecessary tool wear and the like. Thus, the conventional machining of thin parts from solid blocks (i.e. plate stock), for example, such as is done in the aerospace industry, is simply not adequate. It is desirable that machining, especially of difficult-to-machine and expensive materials, be insensitive to the thinness of the finished components.